As an analyzer that analyzes the amount of a component contained in a sample (hereinafter also referred to as “specimen”), there has been known an automatic analyzer that measures the amount of transmitted light or the amount of scattered light with a single wavelength or a plurality of wavelengths obtained by irradiating light from a light source onto a reaction mixture obtained by mixing a sample with a reagent, and calculates the amount of the component based on the relationship between the amount of light and the concentration. In the reaction of the reaction mixture, there are roughly two types of analysis fields as follows: a colorimetric analysis using a coloring reaction between a substrate and an enzyme; and a homogeneous immunoassay using an agglutination reaction by binding of an antigen to an antibody. As the latter homogeneous immunoassay, there have been known measurement methods such as an immunonephelometric method and a latex agglutination method.
In an immunonephelometric method, a reagent containing an antibody is used, and an immune complex of the reagent with a measurement target (antigen) contained in a sample is formed, the resulting immune complex is optically detected, and the amount of a component is quantitatively determined. In a latex agglutination method, a reagent containing latex particles sensitized (bound) with an antibody on the surfaces thereof is used and the latex particles are agglutinated by an antigen-antibody reaction with an antigen contained in a sample, the resulting agglutinated particles are optically detected, and the amount of a component is quantitatively determined. Further, there has also been known a heterogeneous immunoassay device that performs an immunoassay with higher sensitivity by employing a detection technique using chemiluminescence or electrochemical luminescence and a B/F separation technique.
In addition, there has also been an automatic analyzer that measures a blood clotting ability. Blood maintains its fluidity in blood vessels and flows therethrough. However, once bleeding occurs, a clotting factor present in plasma or platelets is activated in a chain reaction, and fibrinogen in plasma is converted to fibrin, and the fibrin is deposited, whereby bleeding is arrested. Such a blood clotting ability includes an extrinsic one in which blood leaking outside the blood vessel clots and an intrinsic one in which blood clots in the blood vessel. The measurement items with respect to the blood clotting ability (blood clotting time) include a prothrombin time (PT) in an extrinsic blood clotting reaction test, an activated partial thromboplastin time (APTT) and a fibrinogen level (Fbg) in an intrinsic blood clotting reaction test, and the like.
For all these items, it is necessary to sufficiently stir a mixed liquid of a sample and a reagent for allowing a blood clotting reaction to stably proceed. Therefore, in PTL 1, as a general stirring method in an automatic analyzer, a method of performing stirring by immersing a stirring bar in a material to be stirred is described. In addition, in PTL 2, non-contact stirring is realized by stirring a sample and a reagent with ultrasound, and therefore, a risk of carrying a component of a material to be stirred in a material to be stirred subsequently is eliminated. Further, if an air bubble is entrained in a mixed liquid when a reagent is added to a sample, disturbance caused by this air bubble may hinder accurate optical measurement, thereby reducing accuracy of measuring a blood clotting ability. Therefore, PTL 3 discloses as a method of preventing air bubble entrainment in a mixed liquid when a reagent is dispensed into a sample, a technique for dropping a reagent along the inner wall of a reaction vessel when the reagent is dispensed by using a dispensing mechanism in which the tip of a nozzle has a substantially circular arc shape when the reagent is dispensed into the sample.